My vague understanding based on "stuff I've heard or read at various points" is that you can stuff up to like 80-85% wind+solar on a grid before you start having real problems with the fluctuations in production.

If my vague recollections are recollecting something that was correct and not BS when I heard it, Scotland might be fine with it's ~17% nuclear, replacing the remaining 30% gas with more wind+solar.